The present invention relates to a prefabricated building module, a method for constructing a building from the prefabricated building modules and the building formed therefrom.
Modular construction of buildings has been used for many years as one means for reducing construction time and expense. Modular construction has the advantages that the modules can be prefabricated at some remote place such as a factory and subsequently transported to the building site where the modules can be assembled into a building. Thus, the advantages afforded by modular construction are more fully realized when the module is relatively easy to construct thereby reducing the expense of prefabricating the module. The advantages are further realized when the weight of the module is reduced as much as possible so that the module can be easily handled and transported to the construction site. However, the structural integrity of the module cannot be imparied in order to reduce the weight of the module, and a compromise is necessary to provide a lightweight module which also has sufficient strength and rigidity that will permimt it to be handled and transported without damage to the module. The weight and structural integrity of the module are also important when modules are assembled at the construction site. For example, in a tall building, the modules forming the upper story of the building would have to be hoisted several hundred feet before they can be placed into position on the top of the building.
Another advantage of modular construction of buildings is that it affords an opportunity for the concrete superstructure of the building to be formed around the modules, thus eliminating the need for concrete forms to be assembled and removed as the building progresses. Known building modules have been designed which attempt to incorporate each of the above advantages afforded by modular construction. For example, two such known modules are described in U.S. Pat. No. 3,331,170, issued July 18, 1967, and U.S. Pat. No. 3,514,910, issued June 2, 1970.
Although generally satisfactory, known modules do not take sufficient advantage of the opportunities afforded by modular construction. By way of example, known concrete modules are not relatively easy to prefabricate and they are not sufficiently lightweight, but yet rigid to keep the manufacturing and transportation costs competitive with other forms of building construction. Further, since the weight of a typical concrete module having a floor space of about 270 square feet would exceed 10 tons, heavy duty hoisting equipment such as a crawling crane must be used to assemble the modules at the construction site. Therefore, the heavy duty hoisting equipment must generally remain at the construction site until the modules for the upper story of the building have been positioned, which could easily require many months. The expense of having such heavy equipment at the construction site significantly increases the total construction cost of the building. Finally, the total height of a building constructed with known modules would be limited by the boom length of available crawling cranes which is typically less than 220 feet.